The overall objective of this research is to develop a model system for the investigation of metabolic disease resulting from keto acid imbalances. This will be accomplished by growing bacteria (Pseudomonas species) on the branched-chain amino acids and related metabolites as sole source of carbon and energy. The resultant intracellular metabolite imbalances will approximate the physiology of mammalian cells which are unable to catabolize branched-chain amino acids. Preliminary investigations have shown that pseudomonads cultured under these conditions undergo changes in their readily extractable lipids and consequently undergo changes in their antibiotic sensitivity. The next immediate objective is to identify and characterize the lipids responsible for these alterations. Other membrane-related phenomena such as transport, energy production, and peptidoglycan metabolism will be investigated to determine how they are influenced by this nutritional environment. Lipogenesis and branched-chain amino acid catabolic pathways are connected via branched-chain keto acid dehydrogenase which converts keto acids to acyl-Coenzyme A derivatives. This enzyme will be purified and characterized. Mutants blocked in keto acid catabolism and regulatory mutants not subject to branched-chain amino acid inhibitions will be used.